Use of selected fatty alcohols and their mixtures with carboxylic acid esters as lubricant components in water-based drilling fluid systems for soil exploration

ABSTRACT

The invention relates to the use of linear and/or branched fatty alcohols containing at least 12 carbon atoms in the molecule and/or to the use of mixtures of such fatty alcohols with carboxylic acid esters as a lubricating additive in water-based drilling fluids for their use in geological exploration by drilling. The fatty-alcohol-based lubricants or lubricant systems are particularly suitable for use in water-based alkali metal silicate drilling muds which are known to be distinguished by comparatively high pH values. The additives according to the invention combine their lubricating effect with a foam-suppressing effect, i.e. prevent unwanted foaming.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to water-based drilling fluids of thetype used in particular as so-called drilling muds in geologicalexploration by drilling. In the following, the invention is describedwith reference to pure water-based drilling fluids and drilling mudsbased thereon. However, the modification according to the invention ofauxiliary fluids of the type in question is by no means confined to thisparticular application and may also be applied in particular toauxiliary fluids for tackling problems arising from differentialsticking, more particularly to spotting fluids and to fluids used forworkover stimulation and comparable geological drilling applications.

2. Discussion of Related Art

In the relevant technology of the geological exploration of, forexample, oil and/or gas occurrences, there are three basic types ofauxiliary fluids, more particularly corresponding drilling muds, used inpractice, namely: oil-based systems which generally comprise acontinuous oil phase mixed with a disperse water phase in the form ofso-called w/o invert muds, water-based oil/water systems in which theaqueous phase with its dissolved and dispersed auxiliaries forms thecontinuous phase and the oil phase is dispersed therein in the form of afine emulsion and, finally, pure water-based drilling fluids.

The pure water-based systems are the oldest in the historicaldevelopment of drilling fluids. However, their use is attended by suchserious disadvantages that, hitherto, only limited application has beenpossible. Above all, the interaction of the water-based drilling fluidswith the water-sensitive layers of rock—more particularly correspondinglayers of clay—to be drilled leads to unacceptable interference with thedrilling process.

Very recently, however, a fairly old proposal has been taken up againand, even in highly sensitive shale formations, can lead to adequatestability where purely water-based drilling fluids are used. It involvesthe use of corresponding systems based on soluble alkali metal silicateswhich are also known as waterglasses or waterglass-based systems, cf.for example the seminar on “The Prevention of Oil Discharge fromDrilling Operations” held in public in Aberdeen on 18th/19th June 1996(organized by IBC Technical Services, London) and, in particular, thepublications appearing in this connection by M. Eigner entitled “FieldTrials with a Silicate drilling Fluid in Shell-Expro” and by I. Ward andB. Williamson entitled “Silicate Water Based Muds—a Significant Advancein Water Based Drilling Fluid Technology”.

However, the use of purely water-based drilling fluids, particularly ofthe last-mentioned type, makes the presence of components with alubricating effect desirable. Relevant specialist knowledge is relevantin this regard. It is known that carboxylic acid esters have aparticularly pronounced lubricating effect which is utilized in manyrespects in geological exploration. However, their use in water-basedsystems and, in particular, in comparatively highly alkaline waterglasssystems can lead to serious difficulties. Ester cleavage can result inthe formation as secondary products of components with a marked tendencyto foam which then introduce unwanted problems into the drilling fluid.The above-cited publication by I. Ward et al. refers specifically tothis problem.

The problem addressed by the present invention was to provide lubricantsfor water-based drilling fluids and, more particularly, for high-pHsilicate-containing waterglass-based drilling fluids which would be atleast partly stable to hydrolysis, but which at the same time would alsoenable carboxylic acid esters to be used if required and would thuspreclude the adverse effects of potential hydrolysis through theirpronounced foam-suppressing effect.

SUMMARY OF THE INVENTION

A The present invention relates to the use of selected linear and/orbranched fatty alcohols containing at least 12 carbon atoms in themolecule and to the use of mixtures of these fatty alcohols withcarboxylic acid esters as a lubricating additive in water-based drillingfluids for their use in geological exploration by drilling.

More particularly, the invention relates to the use of thesefatty-alcohol-based lubricants as an additive in water-based alkalimetal silicate drilling fluids.

Particulars of the Teaching According to the Invention

In the course of the development work for new water-based drillingfluids, it was found that special alcohols have favourable lubricatingproperties in such drilling fluids. Fatty alcohols of the type accordingto the present invention have the additional advantage that they arestable even in highly alkaline water-based fluids. Because of this, theywere also tested in particular in modern silicate drilling fluids(waterglass systems).

It was surprisingly found that certain fatty alcohols of the typeaccording to the invention—described in detail hereinafter—exhibitextremely good lubricating properties even though their lubricatingeffect in other clay-containing water-based drilling fluids is notparticularly remarkable.

The positive effects of the selected fatty-alcohol-based auxiliaries onwhich the invention is based can be further enhanced by using the fattyalcohols together with carboxylic acid esters characterized by goodlubricity. Further observations in this regard will again be madehereinafter. It is remarkable that, despite the expected partial estercleavage and the resulting theoretical danger of an increase in thetendency to foam, there are no unwanted effects in this direction. Thefoam-suppressing effect of the fatty alcohols compulsorily used inaccordance with the invention—in the form of their intimate mixture withthe esters—is evidently so great that the desired advantage of theenhanced lubricating effect can be utilized here without having toaccept disadvantages in the form of increasing foaming in practice. Evenas hydrolysis products, certain selected esters (see the followingdisclosure) provide special effects in helping to solve the problemaddressed by the invention.

The fatty alcohols used in accordance with the invention are firstdescribed in broader and in preferred definitions in the following,after which suitable and particularly preferred ester mixing componentsare similarly discussed.

Fatty alcohols are known to be monohydric alcohols with comparativelylong hydrocarbon chains which in turn may be linear and/or branched.Corresponding fatty alcohols in the C₁₂₋₃₀ range are particularlysuitable, fatty alcohols in the C₁₂₋₂₄ range being particularlypreferred for use in accordance with the invention.

The fatty alcohols may be of natural and/or synthetic origin. It isknown that fatty alcohols of natural origin are obtained from thecorresponding fatty acids by reduction of the terminal carboxyl group tothe alcohol group. The fatty acids of natural origin in the C chainlength range in question are generally present in the form of mixturesof aliphatically saturated and/or olefinically unsaturated acids. Theolefinically unsaturated acids with at least 14 to 16 carbon atoms inthe molecule contain varying amounts of mono- and/or polyolefinicallyunsaturated compounds, depending on the natural material source. Bysuitably selecting the reduction conditions, it is possible to achieveat least substantially specific reduction of the carboxyl group withoutany effect on the olefinic double bonds in the carbon chain so thatcorrespondingly mono- and/or polyunsaturated fatty alcohols, for examplein the C₁₆₋₂₄ range and more particularly in the C_(16/18) range, areavailable. The relevant specialist literature on this subject isrepresented, for example, by the book published by applicants entitled“Fettalkohole, Rohstoffe, Verfahren und Verwendung (Fatty Alcohols, RawMaterials, Processes and Uses)” which contains detailed information onindustrial processes for the production of fatty alcohols, on theanalysis and characteristic data of fatty alcohols and on thephysicochemical properties of these fatty alcohols of natural origin.Linear olefinically unsaturated C_(16/18) fatty alcohols or mixtures offatty alcohols consisting at least predominantly of such components areparticularly suitable for use as the fatty alcohol component inaccordance with the present invention. Systems of the type in questionwhich flow at room temperature can be particularly important althoughthe invention is by no means confined to such systems. Correspondingcommercial products are marketed by Applicants under the registerednames of “HD-OCENOLS”.

Fatty alcohols with a branched carbon chain may be obtained either bypure syntheses, for example including the oligomerization of lowerethylenically unsaturated hydrocarbons, or by dimerization of alcoholsof natural origin to form branched alcohols of the Guerbet type. Thecondensation of comparatively lower primary alcohols by heating attemperatures of 200 to 300° C. in the presence of alkali, for examplepotassium hydroxide or potassium alcoholate, leads to Guerbet alcoholsbranched in the 2-position to the hydroxyl group, cf. applicants'above-cited publication entitled “Fettalkohole . . . (Fatty Alcohols . .. )”.

In the efforts to find a solution to the problem addressed by theinvention, it was found that these Guerbet alcohols and, moreparticularly, corresponding alcohols in the C₁₂₋₂₀ range are extremelyeffective in helping to solve that problem. Particularly importantGuerbet alcohols are those in the C₁₆₋₂₀ range. The constitution ofbranched alcohols of this type makes them flowable at room temperaturewith pour points generally below 0° C.

So far as the fatty alcohol component is concerned, the teachingaccording to the invention may be summarized as follows: on the onehand, olefinically unsaturated alcohols, more particularly in theC_(16/18) range, of the type marketed as “HD-OCENOLS” are particularlypreferred. Of these, oleyl-alcohol-based fatty alcohols or fatty alcoholmixtures are especially suitable. On the other hand, Guerbet alcohols inthe C₁₆₋₂₀ range and more particularly in the C_(16/18) range areparticularly important auxiliaries in the context of the presentinvention. This applies above all to their resurrected use in highlyalkaline waterglass-based silicate drilling fluids.

According to the invention, these fatty alcohols are added on their ownto the water-based drilling fluids. In one preferred embodiment,however, they are used—as previously mentioned—in the form of a mixturewith carboxylic acid esters. It is known that carboxylic acid esters ofvarious types can influence improvements in lubricity, particularly inwater-based drilling muds. General expert knowledge may be applied inthis regard. The more recent prior art is represented, for example, byEP 0 713 909.

Basically, therefore, esters of mono- and/or polybasic carboxylic acidsand mono- and/or polyhydric alcohols are suitable for mixing with thefatty alcohols defined in accordance with the invention. A preferredclass of such esters is based on corresponding reaction products oflinear, optionally olefinically unsaturated and/or branchedmonocarboxylic acids of the fatty range. Preferred acid components ofthis class of esters contain corresponding C₁₂₋₂₄ and, moreparticularly, C₁₄₋₂₀ hydrocarbon radicals in their acid constituent.

As already mentioned in connection with the fatty alcohols, it may againbe desirable in the case of the esters to use components which areflowable at room temperature. This preferred property can be establishedand regulated in known manner in the esters of long-chain fatty acids byproviding an adequate number of olefinic double bonds in the hydrocarbonchain and/or by giving the hydrocarbon chains a branched structure.Accordingly, corresponding esters of fatty acids of natural and/orsynthetic origin which meet the above-mentioned parameters are suitablefor use.

The ester-forming alcohol components may be monohydric and/orpolyhydric. Among the monohydric ester-forming alcohols, correspondingfatty alcohols are particularly important. The special definitions givenabove in connection with the fatty alcohol component again apply togeneral and preferred representatives. Accordingly, esters of C₁₂₋₂₄and, more particularly, C₁₄₋₂₀ fatty alcohols are particularly suitable.Mono- and/or polyolefinically unsaturated fatty alcohols can again beparticularly important. The foregoing observations on the productsmarketed by applicants as “HD-OCENOLS” again apply.

It will readily be appreciated in this connection that esters whichcontain corresponding long-chain hydrocarbon radicals not only in theirfatty acid component, but also in their alcohol component aredistinguished by particularly good and effect-enhancing lubricatingproperties. In addition, esters of the type discussed here changethrough partial hydrolysis into the essential active component—describedat the beginning—of the lubricants used in accordance with theinvention. Besides the fatty acids released, which are converted intotheir salts in the normally basic water-based drilling fluids, the freefatty alcohols and hence the essential lubricant component according tothe invention are formed. One example of a typical representative ofthis type is oleyl oleate; another is isotridecyl stearate.

Basically, however, esters of alcohols with relatively short carbonchains may also be used, for example fatty acid esters in the C-chainlength range mentioned with monohydric alcohols containing at least 4carbon atoms and preferably at least 6 to 8 carbon atoms. Ester oils ofthis type are now alternative oil phases used on a large scale foroil-based drilling muds. The relevant literature is represented byapplicants' corresponding European patents EP 0 374 671, EP 0 374 672,EP 0 386 638, EP 0 386 636 and EP 0 535 074 which describe particularlysuitable polycarboxylic acid esters for use in oil- and/or water-baseddrilling muds. Further particulars of oleophilic alcohols in drillingfluids can be found in EP 0 391 252 and in EP 0 472 558.

However, other suitable ester components are corresponding compounds of,in particular, lower polyhydric alcohols, for example of the glycol,glycerol or trimethylolpropane type, and lower alcohols containing inparticular up to 6 carbon atoms and a corresponding number of hydroxylgroups. Examples include esters or partial esters of glycoses or loweralkyl glycosides with, in particular, fatty acids having the structuresdefined above. Accordingly, preferred polyhydric alcohols contain up to6 carbon atoms and up to 6 hydroxyl groups in the molecule. In the caseof the polyhydric alcohols, triglycerides, more particularlytriglycerides of natural origin, can be of particular importance. Theyhave proved to be effective mixing components for mixing with the linearand/or branched fatty alcohols defined at the beginning.

Fatty-alcohol-based lubricants or lubricant systems corresponding to theabove definition are generally present in the water-based drillingfluids in quantities of at most 10% by weight and, preferably, in farsmaller quantities. Preferred limits are about 5% by weight or lower.Additions of 0.5 to 3% by weight and, more particularly, 1 to 3% byweight can be particularly effective.

The mixtures of linear and/or branched fatty alcohols with estersoptionally used in accordance with the invention have ester contents ofno more than about 80% by weight and preferably no more than 60 to 70%by weight (% by weight, based on the sum of fatty alcohol and ester).Particularly suitable mixtures of fatty alcohol(s) and ester(s) containaround 25 to 55% by weight of ester, again based on the mixture of fattyalcohol and ester. Mixtures of approximately equal parts by weight canbe particularly suitable.

Water-based drilling fluids and the additives to be used therein, suchas weighting agents, fluid loss additives, alkali reserves, viscositycontrollers and the like, are extensively described in the generalliterature and relevant patent literature. Detailed information can befound, for example, in the book by George R. Gray and H. C. H. Darleyentitled “Composition and Properties of Oil Well Drilling Fluids”, 4thEdition, 1980/81, Gulf Publishing Company, Houston and the extensivescientific and patent literature cited therein and in the manualentitled “Applied Drilling Engineering” by Adam T. Borgoyne, Jr. et al.,First Printing Society of Petroleum Engineers, Richardson, Texas (USA).The water-based silicate muds with which the teaching according to theinvention is particularly concerned are also general expert knowledge,cf. in particular the relevant publications cited at the beginning.Basically, suitable alkali metal silicates are, in particular,water-soluble sodium silicate and/or water-soluble potassium silicatewith modulus values (molar ratio of SiO₂ to Na₂O or K₂O) of 1.0 to 3.3and preferably 1.5 to 2.5. Preferred concentrations of the alkali metalsilicates in the water-based fluids are at most about 10% by weight andpreferably slightly lower, for example in the range from about 3 to 8%by weight and preferably in the range from about 4 to 7% by weight. Thealkali metal silicates are normally accompanied by high concentrationsof soluble nonreactive salts, more particularly alkali metal chlorides(especially sodium and/or potassium chloride), in the water-based fluidphases. Correspondingly salt-saturated water-based silicate muds arepreferred in practice. The pH values of these liquid phases are,comparatively speaking, in the strongly alkaline range and are above pH10 and, more particularly, are at least at pH 11. It is in this class ofhighly alkaline silicate muds that the lubricants according to theinvention have proved to be particularly effective when added in smallquantities of, for example, 1 to 3% by weight, based on the mud as awhole. So far as the resurgent use of these purely water-based systemsis concerned, it is possible by using very small quantities of organiccomponents selected in accordance with the invention to achieve asubstantial improvement in performance equivalent to that known inprinciple for the use of components with a lubricating effect inwater-based systems.

According to the invention, it may be advisable to secure and/or improvethe lubricating effect of the added component even under workingconditions involving extreme pressure. There are various known additivesfor such working conditions, so-called extreme-pressure additives, whicheffectively secure improved lubrication in such conditions.

The prior-art literature in this regard is represented by “Ullmann'sEncyclopedia of Industrial Chemistry”, 5th Edition, Volume A15, Chapter“Lubricants and Related Products” and the associated Sub-chapter 7.5“Extreme-Pressure Additives” (loc. cit., pages 450/1). An additionaldisclosure in this connection can be found in Sub-chapter 4.4“Phosphoric Acid Esters”, loc. cit., pages 440/1.

These literature references describe many representatives ofextreme-pressure lubricants from a plurality of classes of at leastpredominantly organic compounds. The following representatives inparticular are named: P-containing organic compounds, for examplearomatic and/or aliphatic esters—including corresponding partialesters—of acids of phosphorus and/or partial salts thereof, for examplecorresponding phosphates and/or phosphonates; sulfurized organiccompounds in which polysulfidic bridge elements in particular yieldsulfur accessible under in-use conditions for covering/reacting off withmetal surfaces, for example sulfurized hydrocarbon compounds, sulfurizedester oils, corresponding fatty alcohols, fatty acids and the like;organic nitrogen compounds, such as aromatic nitro compounds,aminophenol derivatives, esters of carbamic acids, salts of organicbases with organic acids and, finally, organohalogen compounds.

Multicomponent additives in which two or more of the classes ofcompounds mentioned are mixed or combined in the molecular structure areparticularly effective. Combinations of sulfur-, phosphorus- and/ornitrogen-containing additives are particularly suitable.

Where additives of the type in question, particularly extreme-pressureadditives, are used, they are normally added to the lubricatingadditives or mixtures according to the invention in small quantities.

EXAMPLES

The following Examples compare the values determined by measurement fora number of lubricant compositions corresponding to the teaching of theinvention with the same measured values of a blank test where nolubricant is added.

In every case, the water-based drilling fluid used is a waterglass-basedsodium silicate fluid having the following composition:

Saturated aqueous sodium chloride solution 253 g 40% by weight aqueouswaterglass solution 59.4 g (sodium silicate with a modulus of about 2.2)Xanthan polymer 0.4 g Dry starch in the form of a fine powder 8.5 gWater-soluble amine component 1.7 g Barite 176 g

The lubricating effect is numerically determined in the commerciallyavailable standard device (“Reichert frictional wear balance”) which canbe obtained together with the necessary instructions for use andevaluation of results through the firm “SUR-Berlin”, Sommer & Runge KG,D-1000 Berlin 48, Symeonstrasse.

The following comparison tests determine the particular friction-wornarea measured per test formulation in mm² and also the final temperatureassumed by the tested fluid sample in the particular test.

The identical operating conditions in all tests in the frictional wearbalance are: 200 metres covered under a load of 1500 p.

The lubricant additives according to the invention identified in thefollowing Examples are added to the aqueous waterglass-based test fluidin a quantity of 3% by weight. In every case, the mixing ratio of fattyalcohol to ester is 1:1 (parts by weight). The Examples may besummarized as follows:

Comparison Example

No lubricants added.

Example 1

Addition of a Lubricant Mixture of C₂₀ Guerbet Alcohol/oleyl Oleate

Example 2

Addition of a Lubricant Based on a Mixture of Oleyl Alcohol (Mixed withSmall Amounts of Distillation Residue)/Oleyl Oleate

Example 3

Addition of a Lubricant Based on the Oleyl Alcohol Used in Example2/Isotridecyl Stearate

Example 4

Addition of a Lubricant Based on C₁₆ Guerbet Alcohol/isotridecylStearate

Example 5

Oleyl-alcohol-based Lubricant of Example 2, but Without the Oleyl Oleate

The abrasion values in mm² (average of 3 measurements) determined in theindividual tests are set out in the following Table together with thefinal temperatures of the test fluid phases.

Abrasion in mm² Temperature effect Examples (3x determination) in ° C.Comparison Example 6.0-6.5 54-55 1 4.0-4.5 44-46 2 4.5-5.0 45-46 35.3-5.6 47-48 4 4.4-4.8 47-49 5 4.8-5.3 43-44

The lubricating effect of the additives according to the invention isreflected both in the reduction of the worn areas and in the reductionof the final temperature assumed by the tested fluid phase.

What is claimed is:
 1. A water-based drilling fluid comprising: a) 0.5to 5 percent by weight of a fatty alcohol-based additive comprisinglinear or branched monohydric fatty alcohol having at least 12 carbonatoms; b) a soluble alkali metal silicate; and c) water.
 2. Thewater-based drilling fluid of claim 1 wherein the fatty alcohol-basedadditive is present at from 1 to 3 percent by weight based on thewater-based drilling fluid.
 3. The water-based drilling fluid of claim 1wherein said fatty alcohol contains from 12 to 30 carbon atoms.
 4. Thewater-based drilling fluid of claim 3 wherein said fatty alcoholcontains from 12 to 24 carbon atoms.
 5. The water-based drilling fluidof claim 1 wherein said fatty alcohol is a mono- or polyolefinicallyunsaturated C₁₆₋₂₄ fatty alcohol.
 6. The water-based drilling fluid ofclaim 1 wherein said fatty alcohol is a C₁₂₋₂₀Guerbet alcohol.
 7. Thewater-based drilling fluid of claim 6 wherein said fatty alcohol is aC₁₆₋₂₀ Guerbet alcohol.
 8. The water-based drilling fluid of claim 1wherein said fatty-alcohol-based additive is flowable at roomtemperature.
 9. The water-based drilling fluid of claim 1 wherein thefatty alcohol-based additive further comprises a carboxylic acid ester.10. The water-based drilling fluid of claim 9 wherein said fattyalcohol-based additive comprises up to 80 percent by weight carboxylicacid ester.
 11. The water-based drilling fluid of claim 10 wherein saidfatty alcohol-based additive comprises up to 60 percent by weightcarboxylic acid ester.
 12. The water-based drilling fluid of claim 11wherein said fatty alcohol-based additive comprises 25 to 65 percent byweight carboxylic acid ester.
 13. The water-based drilling fluid ofclaim 9 wherein said carboxylic acid ester is the reaction product of amono- or polybasic carboxylic acid with a mono- or polyhydric alcohol.14. The water-based drilling fluid of claim 13 wherein said carboxylicacid is a linear monocarboxylic acid containing from 12 to 24 carbons.15. The water-based drilling fluid of claim 14 wherein said linearmonocarboxylic acid contains from 14 to 20 carbons.
 16. The water-baseddrilling fluid of claim 13 wherein said carboxylic acid ester is thereaction product of C₁₂₋₂₄ monocarboxylic acid with C₁₂₋₂₄ monohydricalcohol.
 17. The water-based drilling fluid of claim 16 wherein saidcarboxylic acid ester is the reaction product of C₁₂₋₂₀ monocarboxylicacid with C₁₂₋₂₀ monohydric alcohol.
 18. The water-based drilling fluidof claim 17 wherein said carboxylic acid ester is the reaction productof C₁₂₋₂₀ monocarboxylic acid with C₁₂₋₂₀ monohydric alcohol.
 19. Thewater-based drilling fluid of claim 13 wherein said carboxylic acidester is the reaction product of C₁₂₋₂₄ monocarboxylic acid with apolyhydric alcohol containing up to 6 carbon atoms and up to 6 hydroxylgroups.
 20. The water-based drilling fluid of claim 19 wherein saidcarboxylic acid ester is the reaction product of C₁₂₋₂₀ monocarboxylicacid with polyhydric alcohol containing up to 6 carbon atoms an up to 6hydroxyl groups.
 21. The water-based drilling fluid of claim 19 whereinthe carboxylic acid ester is a triglyceride.
 22. The water-baseddrilling fluid of claim 1 wherein said fatty-alcohol-based additivefurther comprises an extreme-pressure additive.